Safety-valve.



G. H. CLARK.

SAFETY VALVE.

PPLICATION FILED MAR. 31. I916. 1,231 Patented June 26, 1917.

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CLARK, OF CAMBRIDGE, MASSACHUSETTS, ASSIGNOR T CROSBY STEAM seen & vervecomram, or BOSTON, MASSACHUSETTS, A conroaarron or Massasarnrv-vanvn.

OJEEUSETTS.

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To all whom it may concern:

Be it known that I, GEORGE HALL CLARK; a citizen of the United States,and resident of Cambridge, in the county of Middlesex and State ofMassachusetts, have invented new and useful Improvements in Safety-.Valves, of which the following is a specification.

My invention relates to safety valves, and has for its object theprovision of means for adjusting a safety valve both with respect to itsblow down and warning.

Means for adjustment of safety valves in these respects are shown anddescribed in my application for United States patent (Serial No. 77,318,filed-February 9 1916) for improvements in safety valves, in associationwith the standard orifice safety valve which comprises the chief subjectmat- 2o ter of that application, and such adjustment means are thereinclaimed in that association.

Blow down and warning adjustments, exemplifying my invention, are notconfined .to association with standard orifice safety valves, but may'with advantage and utility be applied to safety valves of .VaIlOllStypes.

hese Improvements are therefore described herein in association with astandard ori- 3o fice. type of valve,

said application, and also 1n assoclatlon with a safety valve of theordinary commercial type.

illustrate examples of my inve'ntion,-

Figure 1 shows, in section, part of a standard orifice down and warningadjustments;

Fig. 1 shows, in sect1on, parts of the base annular surfaces arenon-adjustable; 1 shows, in section, parts of the base andv disk of avalve, wherein the two cong annular surfaces are adjustable only Fig. 2,shows, in section,'part of an ordi- U naryz-eoercial safety valve, withblow ""Edown?{and warning adjustments; and I. ig. 2* 'shows, in section,parts of the base I to and diskof a valve,"where1n the inner congtrolling annular." surface is he'outer one adjustable.

iiFig l, partsof thevalvedisk D-and "areshowmthe valve spring, casingnon-adjustable,

Specification of Letters Patent.

such as disclosed in my' In the drawings hereto annexed, which safetyvalve, with blow and disk of a valve, wherein the controllingspectively. The actual seat of Patented June 26, 31911 X.

' Application filed March 31,1916. Serial 1V0. 87,928.,

ated in safety valve construction are well own, and not shown here. Fig.1 represents a standard orifice safety valve, such as described in mysaid application.

or presentpurposes it will sufiice to deco scribe the characteristics ofa standard origas under pressure (such as steam) will, in escapingthrough the orifice completely fill 05 I all portions thereof, and exertmaximum pressure on the sides of the orifice, (this of the absoluteboiler pressure) up to a point near v the discharge end, where it fallstoward the 7o external, or back, pressure. A cylindrical less than thediameter of the orifice itself, and this diameter will be uniform, fromthe throat (or entrance) to the lips at the discharge end.

Thus, a standard orifice safety valve is one which, at a predeterminedvalue of lift (by calculation subject to empirical correcso tion)provides an escape orifice which is completely filled by escaping steam,and of which the effective 'cross sectional area at the throat (orentrance) is approximately equal to the e ective cross sectional area atthe lips (or discharge end).

his condition is fulfilled by a disk and ase having curved opposedsurfaces, which y from the valve axis progressively approach parallelismto that axis. his conditi'en involves the maintenance of maximum lateralpressure on the orifice-surfaces, the maximum lifting effect on thevalve disk is secured andmaximum discharge eficiency a valve of thisstandard modified, would possess the practical defect of large blowdown.

Referring again to Fig. 1: The valve base is provided with twoconcentric rings, W 100 R, each adjustably mounted by means of a screwthread connection, at T and T, rethe diskD to insure the permanentlocaorlfice type, unless is at S; and

tion of the seat at this point, the annular lea ttle higher thanportions of the'base surface lying outside discharge and respectively,and are so proportioned as to produce 113.

maintained. But

escape passage between the standard orifice condition in the the disk Dand the base B taken in conjunction with the rings W and R. The rings Wand R are so shaped that when screwed up close to the disk-surface Dthey, with the base B, present a surface parallel, or coincident, withthe surface D The surface D curving toward parallelism with thevalve-axis, terminates at the lip d, which lies opposite the lip b inring R.

With both rings W and R moved up to form a continuous surface with thetop of the base B, the valve constitutes a standard orifice valve,without modification. At a predetermined lift-value, the efiectivecross-sectional area of orifice at the throat at S will equal that atthe lips I), d, and as observed above, such a valve will have a verylarge blow down.

But if the ring W, carrying the ring R, be backed off a little, so thatan initial enlargement of the orificial space extends from the thread Toutward to the lips I), (Z, the detriment due to large blow down will beobviated, and the blow down reduced practically to any value desired.Such an adjustment as this would in substance treat the two rings W andR as one, and both together would operate as a means for adjusting theextent of blow down. And, to compensate for the initial clearanceproduced bybacking off the rings, the outer ring and its curvaturetogether with the curved disksurface should be extended far enough toproduce equality in cross sectional area as between the throat .and lipsof the orifice, when the predetermined value of lift is reached.

Treating the two rings W and R as one, by moving the ring away from thedisk, the blow down will be reduced. But when the two rings (acting asone) are adjusted to give small blow down, the drop in pressure duetoenlarged clearance will prevent the valve from developing liftingpressure enough-at'initial lift-to raise it promptly; in other words topop. Consequently the warning of the valve willbe unduly prolonged.

Herein lies the functional value of the two-ring arrangement. The innerring W, which in the example shown may be called the warning ring, ifbacked away but slightly from a position flush with the basesurface,insures retention of the actual seating surface within a region close tothe throat of the discharge orifice between the disk and base, while atthe same time conserving to a substantial degree the lifting effect ofpressure on the disk-surface immediately opposite to the surface of thering W. The closer ring W lies to the disk surface D the shorter will bethe warning, and the quicker the pop and vice versa. Then, in order toreduce blow down, the ring For illustration, Fig. 1

B may be backed off to a relatively great distance; as with a singleblow down ring, the farther ring R is adjusted from the disk D, thesmaller will be the blow down, and vice versa.

In practice, a mode of making adjustment will be to start with thewarning ring flush with the base (or backed away enough to make surethat the seat is on the base and near the throat) and back off the blowdown ring R until the desired blow down range is secured empirically.Then back off the warning ring W until the desired degree of warning issecured. This adjustment of the warning ring will have no appreciableeffect on the blow down; while if the blow down ring alone bereadjusted, its readjustment will have no appreciable effect in thewarning.

While the adjustable rings are tov be preferred, the base (or the disk)of a valve may be formed integrally with annuli of calculated clearanceand radial proportions, to secure an acceptable permanent condition inrespect to warnlng and blow down. That is to say, the adjustment may bemade once for all by appropriately designing the surface of the base (ordisk) or it may be made variable by providing ad ustable annuli in theshape of a warning ring and a blow down ring each of which will, inusual practice, be'finally fixed in that position of adjustment whichaffords shows a valve disk and base, in which the warning annulus W andblow down annulus R are surfaces parallel withthe opposite orificialsurface, but spaced therefrom.

A double adjustment of the same kind may be efiected in a safety valveof the type heretofore generally employed; such a valve is shown in itsessential parts, in Figs. 2 and 2. Here the disk D and base'B are formedwith conical engaging surfaces, and the disk D is extended to furnishthe chamber C between the seating cone and the lip 01, while the base Bis outwardly flanged, terminating in the lip b. In such a valve,theextent of warning is determined by the extent of conical surfacesopposed near the actual seat, the larger this surface, the shorter thewarning. And, in such a valve, the extent of blow down is determined bythe initial degree of separation between the lips I) and d; thisseparation has been made adjustable in many safety valves heretofore andstill in the market.

By providing an adjustable warning ring W, part at least of whosesurface lies within the region of opposed conical surfaces near thevalve seat, the degree of warning may be adjustably determined.Retraction of the warning rin to a slight distance from the opposite surace has the same effect as would a diminution of the conical opposedsurfaces.

the desired results.-

1,2e1,eso

The warning ring may be so far withdrawn that its surface ceases to haveany effect on the warning, leaving only the fixed portion of the base todetermine the length of warn- 1ng.

And, as in the case of the valve'illustrated in Fig. 1, the warningadjustment is independent of the blow down adjustment.

Or, if it be desired to have the blow down annulus adjustable, the ing'fixed at a predetermined clearance, the blow down ring may be adjustablymounted outside the warning annulus, as illustrated in Fig. 2*, whereinthe fixed predetermined Warning annulus is shown at W, and theadjustable blow down ring at R.

It is, however, conceivable that the adjustblow down ring Rmay e fixedonce for all in relation to the warning ring, and thereafter be movedwith the Warning g a the latter is adjusted, as is shown in Fig. 1

Whatever respects to a nicety, and increases the adaptability of a.valve to a miscellany of requirements which heretofore have been metonly approximately, or if met fully, have demanded special designs andconstructions with consequent increase of cost.

In any valve there Will be found a specific feature or factor whichdetermines the blow which determines the warning. In adapting thisinvention to any valve, therefore, the equivalent of the blow down ringsabove described will be found in a member which comprises the feature orwarning annulus befactor determinant of blow-down range, and likewise,the equivalent'of the warning rings above described will befound in amember which comprises the feature or factor determinant ofwarningrange. And, within practicable limitations, these factors may beincorporated in the base or the disk, or it may be, in both. of theseprincipal members of a safety valve. I

For most situations, both the blow down annulus and the warning annulusshould be made adjustable, and it is preferable that they shouldbeindependently adjustable.

What I claim, and desire to secure by Letters Patent is: 1

1. In a safety valve, the combination with the disk and base, of awarning annulus and a blow down annulus, and means for adjusting thesaid annuli.

.2. In a safety valve, the combination with the disk and base, of awarning annulus and ablow down annulus, and means for adjusting eitherindependently of the other.

- In a safety valve, the mutually-seating disk and base members, awarning annulus on one of said members outside the seat, havnulus,outside the warning annulus, and

Signed by me at Boston, ltdassachusetts,

this 29th day of March, 1916.

GEORGE HALL CLARK.

